The present invention relates to sewing machines, and more particularly to programmed controlled automatic sewing machines.
Sewing machines having a work holder for moving a work piece through a predetermined pattern relative the machine's sewing needle are known. Such machines are particularly useful when the same pattern is stitched repetitively. The earliest of such automatic sewing machines are relatively complex cam controlled devices in which the entire cam apparatus must be replaced and time-consuming adjustments must be made whenever it is desired to change a machine from one sewing pattern to another. Certain of the cam controlled machines, such as those for sewing buttonholes and tacking, have no capability at all for conversion to other stitch patterns.
More recently, sewing machines have become available in which the work holder is moved according to a sequence of instructions stored in a mechanically controlled element such as a punched paper tape, cards, or a magnetic tape. In such machines, the sequence of instructions in the recording medium controls the movement of the work holder during the portion of each needle cycle when the needle is out of the work piece.
Automatic sewing machines with work holders using paper or magnetic tape or cards to control their movement, however, suffer certain disadvantages. First, the tape and card machines move relatively slowly from one location of stored information to the next location. Accordingly, for the machine to work fast enough, a complete instruction must be placed in a single storage location. Further, the complexity of the operation of the sewing machine is limited by the amount of information which can be placed in each such location. A second limitation, mechanical in nature, exists since the sewing machine speed is limited by the speed at which the storage medium can be physically moved from one storage location to the next. Third, a paper or magnetic tape or card reader is relatively costly in comparison to cam controlled machines. Further, although buffer units to enable faster operation are available, they considerably increase the expense of the system.